The present invention relates to a system for monitoring and visually displaying the degree of refrigerator door usage occurring between defrost cycles in a way that enables a user to conserve on refrigerator energy consumption by changing his or her usage habits in terms of the number of times the refrigerator doors are opened and the length of time the doors are held open.
It is known in the prior art to provide systems, primarily electromechanical in nature, that sense when a refrigerator door is opened and that are able to accumulate the amount of time the door is held open. Generally, the systems of this type are used to reduce the amount of time between defrost cycles in a demand defrost system so as to cause the refrigerator to be defrosted more often in response to heavier usage of the refrigerator. It is also known to provide visual indicators for refrigerators such as lamps to indicate, for example, when a defrost cycle is in operation or when a power failure has occurred and also, for example, to indicate when a freezer door has been left slightly ajar inadvertently. However, there is no known system which monitors the number and duration of door openings to provide a visual indication to the user that would enable the user to change his or her usage habits in the direction of conserving energy consumption by the refrigerator.
The number of door openings and the amount of time the door is held open has a direct bearing on the amount of energy usage by the refrigerator both in terms of compressor run time needed to maintain the desired cool temperatures in the refrigerator and of the timing of defrost cycles needed to remove frost from the evaporator coils in the refrigerator. Consequently, the door usage monitor of this invention has utility in refrigerators to reduce energy consumption generally by enabling the user indirectly to control the compressor run time needed to maintain cool temperatures in the refrigerator. Since the defrost cycle in an automatic defrost refrigerator represents a major element of energy usage, the invention has particular utility in a demand defrost usage refrigerator in which the timing of defrost cycles is determined by the number of door openings and/or the amount of actual door open time. In demand defrost refrigerator systems, if there are no door openings, the time interval between defrost cycles is at a maximum and the minimum amount of energy for defrosting will be used over an extended time period. As the doors are opened periodically, the defrost cycle time interval is reduced as determined by the demand defrost system until a minimum time interval between defrosts is reached thus using a maximum amount of energy for defrosting on an ongoing basis. Consequently, it can be seen that a door usage monitor system can be effective in reducing refrigerator energy usage by encouraging decreased door usage in order to reduce compressor run time and also, in a demand defrost refrigerator, to stretch out the interval between defrost cycles.